Conventional hybrid vehicles or hybrid electric vehicles (HEV) reclaim kinematic energy in electrical form while driving and store this energy in an electrical energy store such as e.g. a high-voltage (HV) battery, which may be achieved for example by recuperating energy while the vehicle is driving.
PHEV is characterized by the fact that it offers the possibility of charging the electrical energy store through an external power supply network. As a result, a drive system of a PHEV has two types of energy sources available for producing the required vehicle drive energy: namely, conventional fuel based on fossil energy sources for driving the internal combustion engine as well as electrical energy from the power supply network for driving an electrical drive.
In order to include this in calculating the CO2 emissions of the vehicle, the EU defined a special certification prescription. It has furthermore become clear that in an PHEV the supply from an additional energy source increases the complexity of the control strategy for controlling the energy management that is to be used in a PHEV.
In a PHEV, an electrical energy store is used that has a comparatively high capacity in comparison with an electrical energy store that is installed in a conventional HEV. Hence it is possible to use for a PHEV a charge depleting/charge sustaining (CD/CS) strategy, in which the driving power of the PHEV is initially provided mainly by the electrical energy store until a lower state of charge (SoC) threshold is reached. The stored charge of the electrical energy store is then regulated so as to maintain the low state of charge reached so far. Alternatively, the vehicle may be operated in a mixed mode (“blended mode”), in which the state of charge is regulated in such a way that the available electrical energy is distributed more uniformly over the entire distance traveled.
Document DE 10 2013 220 935 A1 discusses a method for adapting an operating strategy in a hybrid electric vehicle, in which the adaptation of a predictive operating strategy occurs on the basis of ecological and/or economic features of the available energy forms for driving the HEV. For this purpose, the available energy forms are respectively assigned an equivalence factor for converting different forms of energy into one another.
The calculation of a setpoint curve that is as efficient and CO2-economizing as possible normally requires a high computation expenditure for the control unit (ECU) of the vehicle. Therefore, there exist a need to improve and simplify the control strategy for operating the PHEV.